Novel brain implant promises digital independence for patients with upper limb paralysis

A wireless, fully implanted, ambulatory motor neuroprosthesis may soon enable patients with upper limb paralysis to use digital devices, finds a new first-in-human study.

“Two participants with flaccid upper limb paralysis due to amyotrophic lateral sclerosis (ALS) and dependent on caregivers used the ambulatory motor neuroprosthesis in conjunction with eye-tracking to control Windows 10 and independently conduct remote communication, online shopping, and banking tasks,” the researchers said.

Through a minimally invasive procedure, the two ALS patients were given the neuroprosthesis, which was implanted in the superior sagittal sinus, beside the primary motor cortex. A subcutaneous pocket in the chest housed the implant lead. Following wound recovery, both patients underwent training, administered by a neuroscientist, that involved attempting a battery of movements, such as clenching the fist, tapping the food, or extending the knee.

The training session also included attempts at mouse-click actions through eye tracking. Performance testing began when participants were sufficiently adept at controlling the interface.

The two participants were asked to undergo a typing task, which involved observing a displayed word, typing it out using an on-screen keyboard, and pressing the enter key. They were assessed according to metrics such as click selection accuracy, information transfer rate, and correct characters typed per minute.

The ALS patients achieved a click selection accuracy >90 percent. Across the 748 selections made by participant 1 over 129 trials, the resulting accuracy was 92.63 percent. Participant 2 made 569 selections over 95 trials and achieved an accuracy of 93.18 percent. [J Neurointerv Surg 2020;doi:10.1136/neurintsurg-2020-016862]

The resulting correct characters per minute for each of the participant was 13.81 and 20.10, respectively. Both participants successfully completed all qualitative everyday tasks posed to them: texting, emailing, shopping, and digital finance.

“The quantitative assessment of modern-day digitally enabled tasks that improve instrumental activities of daily living provides a challenge to the design of future clinical trials assessing efficacy of implantable brain-computer interfaces (BCIs),” the researchers said. In the present study, this was averted by pragmatically choosing performance metrics that could demonstrate independence in the participants.

“A limitation of this approach is that the results may not be generalizable to other patient populations. The population most likely to benefit from this technology include patients with upper limb paralysis, preserved motor cortex, and preserved eye-movements,” they added, pointing out that there is a variety of reasons by which paralysis occurs and that these need to be considered in the design of future trials.

In addition, the present analysis only included two patients, making any broad and definitive conclusions inappropriate, particularly in terms of long-term safety and efficacy.

“Further work is required to characterize the short- and long-term safety profiles as well as establish standardized task performance criteria for meaningful clinical outcomes to inform the design of a pivotal trial,” the researchers said.